In recent years, development of a technology of welding and repair using a friction stir effect is remarkable. Using friction stir welding, a large number of successful examples of welding that could not be performed in the welding of the related art, such as welding between high carbon steels, dissimilar welding of steel and Al alloy, welding between Ti and alloys thereof that requires a high vacuum level for welding, and so on, have been reported. Since friction stir welding is a technology in which Al is used as a target of a material to be welded at the beginning of development, a material that can be relatively easily available, for example, tool steel or the like, can be used for the tool that is used. For this reason, problems related to the tool are focused on a shape of a probe or a shoulder that exerts an influence on a joint, such as a plastic flow, stirring efficiency, or the like.
Meanwhile, in recent years, developments in friction stir welding have been remarkable in a technology of welding or repairing a steel material, a Ti-based alloy or a Ni alloy having a melting point about 1000° C. higher than that of Al. When these materials are welded or repaired, a tool having strength against high temperatures and good abrasion resistance is needed. Until now, tools having high performance at high temperatures such as ceramic-based tools obtained by sintering cBN (cubic boron nitride) or Si3N4 (silicon nitride), metal-based tools such as Ni-based alloys, Co-based alloys, Mo-based alloys, W-based alloys, Ir-based alloys, or the like, and so on, have been developed, and welding of metals having a high melting point come to be realize.
Since such a tool formed of an Ir-based alloy or the like is generally expensive, a technique of manufacturing only the tool that partially contributes to welding or repair and a holder configured to hold the tool using an inexpensive material and assembling the tool portion and the holder is employed. For example, in Patent Document 1, a tool for friction stir welding having a cutout as a locking section formed at a rear section side of the tool that is detachably attached to a shank part is disclosed. An accommodating section into which a rear section side of the tool having the locking section is inserted is formed in the shank part formed of tool steel or dies steel. As the rear section side of the tool is inserted into the accommodating section of the shank part and a screw that is screwed thereinto is pressed against the locking section of the tool inserted into the accommodating section from a side surface of the shank part, the tool is fixed to the shank part.